The traditional bow hunting method for harvesting large game animals is to kill by exsanguination. The design of conventional hunting arrows has been optimized to produce the most effective method for draining the animal's blood from its circulatory system, thus interrupting the animal's ability to provide adequate tissue profusion. Without an adequate blood supply in the circulatory system, the exchange of oxygen and carbon dioxide at the tissue level cannot continue. The oxygen level then drops and the carbon dioxide level rises until the balance between the two are incompatible with life and the animal expires, achieving the primary goal of harvesting the animal.
However, because the kill is not instantaneous, the game animal has the ability to travel quickly and far from the position it is standing when first struck by the arrow. During the course of its wounded flight, especially in larger animals such as deer or elk, the animal quickly disappears from sight, and the hunter is then burdened with the task of tracking the wounded animal, aided primarily by the blood trail. The blood trail is difficult to follow and so the animal may not be found. The mortally wounded animal may endure unnecessary suffering and may escape to an inaccessible location.
Consequently, improvements in modern hunting arrows for large game animals have been directed to achieving a rapid kill. Some improvements have been directed to maximizing the cutting effect of the arrow head to improve the chance of severing a major blood vessel, thus promoting a quick kill, for example as shown in U.S. Pat. No. 4,762,328. In that patent, a game arrowhead consists of a fixed broad head point with splines that deform and expand upon impact, thus creating greater tissue displacement and trauma effect upon penetration.
U.S. Pat. No. 4,277,067 discloses a hollow arrow shaft which has drainage apertures to promote exsanguination.
U.S. Pat. Nos. 4,252,352; 3,993,311 and 5,314,196 disclose arrows that have a hollow shaft which contain components for enhancing bleeding in a wounded animal and for facilitating tracking the wounded animal.
U.S. Pat. No. 4,277,069 discloses an arrow for blood tracking which includes a tubular shank which is perforated with drainage holes along its length.
Another hunting arrow improvement that represents a departure from the conventional exsanguination technique is disclosed in U.S. Pat. No. 3,617,060. The hollow shaft hunting arrow includes a longitudinal passage which communicates with the atmosphere. When the arrowhead pierces the thoracic wall of the animal, the thoracic cavity is connected directly in communication with the atmosphere by the longitudinal passage. When this occurs, the internal pressure of the thoracic cavity rises from below atmospheric to atmospheric, thus resulting in collapse of the animal's lungs.
Yet another hunting arrow improvement includes apparatus for releasing pressurized air upon penetration, where the pressurized air enhances the cutting effectiveness of the arrowhead, for example as disclosed in U.S. Pat. No. 5,762,574. The hunting arrow has a hollow shaft which is pressurized with compressed air. Upon penetration into the animal, the compressed air is released through vents at a pressure of about 150 psi as a release valve opens. The pressurized air exacerbates the localized wound inflicted by the arrow head, thus accelerating trauma to soft tissue.
Further improvements have included an arrow that is fitted with a cylindrical cartridge containing a chemical drug material that will paralyze, incapacitate or kill a game animal by injecting a drug into the body of the animal upon impact. For example, U.S. Pat. No. 4,463,953 includes a pod carried on an arrow shaft which releases a drug within the body of the game animal upon penetration. A similar arrangement is shown in U.S. Pat. No. 4,726,594 in which a cylindrical cartridge containing a drug is dispensed by a detonator which explodes on impact and injects the drug from the cartridge through a needle into the game animal.